Monster Truck Madness – Completely Overdriven

Brief plug before we get started here – last week I guested on the Radio Impound Podcast! It was a blast talking r/c monsters with hosts Jason Ruona and Gotti Jr.! We discussed my work with Big Squid RC, my monster truck club Trigger King and my time in the full scale monster truck industry. You can check it out right here! Be sure to give them a sub as well, won’t ya?

Last week we discussed Axial SMT10 gearing, and I wanted to talk just a wee bit more about a related subject. Over and Underdrive.

Yeah, this is a popular topic among the r/c crawler crowd, but it’s rarely brought up in the monster truck world.

Luckily for you folks, I have dabbled with both on my SMT10 and I’m here to report my findings.

I specifically wanted to use OD gears to try and get just a bit more speed out of my truck in our strictly regulated “Sport Modified” racing class. My findings? It’s gonna get hot, real hot.

You have to remember that if you put Clod sized tires on an SMT10, you are already “gearing it up” by way of the larger rubber. Adding overdrive on top of that adds even more over-gearing. The bigger problem with this was that Axial HD OD gears do not play well with the differential spider gears, giving them a slight pinch and therefore acting as a limited slip.

All of these factors lead to a truck that was slightly faster, but that got too hot too fast with ill handling to boot, thanks to the diffs. No bueno.

I then decided that for posterity I would throw in a set of UD gears. These fared a bit better as far as launch goes because there was less torque twist. However, it took speed off the top end. Now, that’s usually not a big deal as you can just gear the pinion taller. However, once you go over 18t on the stock setup, room gets very tight on the spur. This means that to offset the loss of top speed I’d need to swap my spur and pinion to another combination. So yeah, this wasn’t worth it to me either, for different reasons.

Now bare in mind that I’m a racer, so some of my associated negatives with each may not be applicable to you, but I found that leaving gearing adjustments to the transmission was the best plan of action.

Hopefully that helps you make a decision if you’ve been mulling it over with your truck!